1. Technical Field
The invention relates to air springs and more particularly, to a swage assembly for sealingly clamping and affixing a resilient elastomeric sleeve member to an end member of the air spring. Even more particularly, the invention relates to a swage assembly which provides for a mechanical interlock between the swage ring and end member to positively locate the swage ring on the end member and to effectively seal the open end of the elastomeric sleeve therebetween.
2. Background Information
Pneumatic springs commonly referred to as air springs, have been used for many applications, including motor vehicles, for a number of years to provide cushioning between moveable parts of the vehicle, primarily to absorb shock loads impressed on the vehicle axles by the wheels striking an object in the road or falling into a depression. The air spring usually consists of a flexible rubber sleeve or bellows containing a supply of compressible fluid and has one or more pistons movable with respect to the flexible sleeve. The piston causes compression and expansion of the fluid within the sleeve as the sleeve compresses and tends as the vehicle experiences road perturbations. The spring sleeve is formed of a flexible elastomeric material, usually containing reinforcing cords, and permits the piston to move axially with respect to another piston or end cap secured within opposed open ends of the sleeve.
The open ends of the sleeves are sealingly connected to the piston and/or opposite end cap, and the integrity of this connection is always one of the important and major aspects in producing an efficient and maintenance-free air spring. Another problem with existing air springs and in particular, the swage ring therefore, is that the swage ring will move in its clamped position under dynamic air spring conditions causing movement of the clamped elastomeric material therebetween tending to loosen the sealing engagement and deteriorating the swage integrity and causing ultimate air spring leakage and failure. This ring movement is especially critical during either extreme of rebound or jounce.
Another problem with existing air springs and the swaging of the elastomeric sleeve ends to the piston member and/or end cap is to achieve a sufficiently tight seal which is able to withstand high fluid pressures contained in the fluid chamber without premature leakage or bursting even upon experiencing severe air spring movement and being exposed to the harsh environments on the undercarriage of a vehicle.
Some examples of air springs and ring sealing devices are shown in U.S. Pat. Nos. 3,788,628, 3,870,286, 4,489,474, 4,573,692, 4,629,170, 4,718,650, 4,784,376, 4,787,607, and 4,787,606.
Other prior art air spring constructions include radially extending shoulders formed on the piston member on which the clamping ring seats and sealingly clamps the cut end of the flexible sleeve against a plurality of uniformly raised ribs formed on the axially extending sealing surface of the piston member adjacent the annular shoulder. However, such. constructions present problems in that the clamp ring is not positively positioned on the annular shoulder, and is free to move in an upward axial direction upon the air spring experiencing severe jounce or extended positioning.
Many of the problems discussed above are solved by the clamping arrangement shown in U.S. Pat. Nos. 4,899,995, 4,852,861 and 5,374,037. These patents show the use of a clamp ring having recesses which align with outwardly extending projections formed on the sealing surface of the piston and/or end member in order to position the ring on the piston or end member. Although such clamp ring assemblies do solve many of the problems discussed above and are extremely efficient for many applications, it has been found that for certain air spring applications, especially for larger air springs having high internal pressure, it may not provide the necessary clamping and ring retention.
Therefore, the need exists for a further improved swage ring assembly for air springs which provides increased clamping and sealing at one or both of the open ends of the elastomeric member between the swage ring and end cap and/or piston, and which firmly secures the ring in position to prevent axial movement thereof.
The present invention provides an improved swage ring assembly for air springs, primarily used for motor vehicles, having a piston at one end and an end cap at an axially spaced opposite end, with a flexible elastomeric sleeve extending therebetween and clamped against the respective end cap and piston member by swage rings to form a fluid tight seal therebetween and provide an intervening pressure chamber.
Another feature of the invention is to provide a swage ring assembly in which axial movement of the swage ring is reduced and/or eliminated when operating under dynamic conditions by providing one or both of the swage rings and end members with cooperating annular projections and aligned recesses which provide a positive mechanical interlock between the swage rings and end members free of intervening elastomeric material, to prevent movement therebetween, and maintaining a positive sealing engagement for the elastomeric sleeve swaged therebetween.
A further feature of the invention is that the piston and/or end cap have clamping surfaces formed with a plurality of annular ribs and intervening grooves which act in cooperation with a corresponding number of ribs and grooves formed on the swage ring to facilitate efficient gripping of the elastomeric sleeve therebetween and to alter the direction of the reinforcing cords contained within the sleeve to further increase the clamping effect of the ring, and which assists in locating the swage ring on the sealing surface of the piston member and/or end cap.
Another feature of the swage ring assembly is that the outer surface of the swage ring generally aligns with an adjacent outer surface of the piston or end cap to provide a generally continuous smooth surface between the swage ring and piston or end cap over which the elastomeric sleeve rolls, to provide a smooth interface therebetween to reduce wear on the elastomeric sleeve as it moves along the surfaces of the piston or end cap and swaging ring during dynamic operation of the air spring.
Preferably the swage ring is symmetrical about its center axis enabling it to be mounted on the selected end member without regard to its up or down orientation on the end member; and in which the ribs, grooves and locking projections on the piston and end cap are similar to that of the swage ring, enabling the swage ring cross-section to be used interchangeably on either of the end members.
The swage ring preferably is metal enabling it to be swaged on either of the end members assuming the end members have the same diameters, which members can be metal, a high strength plastic or similar material.
The foregoing advantages, construction and operation of the present invention will become more readily apparent from the following description and accompanying drawings.